I noticed the 26" barrel on the 280AI after I posted.
Do you think 75fps is an accurate decrease though for matching the barrel length?
According to this formula a 30-06 case loses 39 fps when shortened from 26" to 24". Wouldn't a .280AI be affected closer to that number?
http://www.loadammo.com/Topics/October05.htm I listed two different powders because they were listed as the top velocity charge for each cartridge. I wasn't sure comparing same powders would be fair since they are different cases. However I agree that comparing the charge weight on two different powders is misleading, I was really just using a little hyperbole there to have a little fun.
If the formula I referenced is correct, it's still not that much difference between the 7RM and the 280AI when one is discussing long range. At least to my thinking. Sure the 7 RM will top out a little higher, but is that small amount enough to pass on a shot at any distance comparing one to the other?
The numbers I�ve seen indicate an extra inch can add anywhere from 20fps to 50fps to a load � I simply picked a number in the middle. The article you reference shows a couple of things that make sense, 1) the higher the velocity, the greater the difference, and 2) the shorter the barrel the greater the difference. If you don�t like 75fps, the number I chose, the article you reference shows 48fps for a 7mm RM, 24� to 26�, with MV of only 2885fps from a 24� barrel. So, to keep the math easy, let�s call it 50fps instead of 75fps.
That means the adjusted ,280 Rem AI 160g/N560 load would run 2985pfs, still 129fps slower than the Vihta Vouri 7mm RM 160g/N560 load. If we assume a BC of .31 (160g AccuBond), the 7mm RM has a 75 yard advantage in terms of velocity and energy.
The original question was :
Is anybody using a 280 ackley improved for long range, or has anyone used one in the past?
to which I answered �Nope, got a 7mm RM that will do everything a .280 Rem AI will do, and then some.� The fact is that the 7mm RM will beat the 280 everyday in all weights and when it comes to 175�s its 2970fps vs 2828fps per Nosler 6th, a 142fps difference before adjusting for the longer .280 Rem AI barrel and 192fps after doing so (using 50fps as the adjustment factor).
I�m not claiming the .280 Rem is a bad cartridge. Nor am I claiming the difference in capability will make a big difference in the field, as in most cases it certainly will not. Neither one would be my choice for high volume long range target work - I�m building a 6.5-06AI for that - but for the occasional long range hunting shot and using the best loads in each, the 7mm RM will add about 75 yards to what the .280 Rem AI can do in terms of velocity and energy.
Whether that extra 75 yards is important or not is up to the individual shooter. Of course the 7mm RM can always be downloaded to .280 Rem AI velocities...
